David Raffe, professor of the sociology of education, told The TESS he believed Standard grades were now redundant as exams - although some of their curricular content was still valid.
"Scottish reforms have always been pragmatic and cautious and, to some extent, conservative. We need to recognise that externality is going to underline the credibility of any qualification, but its intrinsic benefits are limited at the lower stages," said Professor Raffe.
"The benefit of internal assessment is that it enhances the professional role of teachers and gives them more control over the system. External assessment is usually a constraint on the flexibility of the system.
"We should not move too radically to make changes that could risk devaluing qualifications. But, over time, we can build up confidence in internal assessment through our experience of NABs. We are also talking about types of qualifications where it is their value within the system that matters, rather than the external value."
He agrees with the finding in the recent Organisation for Economic Co-operation and Development report into Scottish schools that Standard grades are irrelevant as an exam to pupils who are doing well at school, and do not serve less academic pupils well either.
But Intermediate courses also need to be reformed, he argues. The internal assessment units, or NABs, tend to prepare pupils for a basic C, so some pupils find the external exam more challenging than they expect; some Intermediate courses have proved better at helping pupils to progress to Higher than others.
Ms Hyslop's vision is that academic pupils should be able to bypass the "next generation" qualification, giving them 12, 18 or 24 months to do their Highers; other, less academic pupils, would follow the new course, although its format has yet to be consulted upon.